In flight control actuation systems there is typically provided high inertia motors that have high speed shafts which make such systems difficult to stop where maximum travel means hard stops. The brake to be described more fully hereinafter will stop an actuation system when it has reached its maximum allowable travel.
A review of the prior art reveals that ball ramp actuated disc clutch mechanisms and disc brake mechanisms are not new. Typical of these just noted mechanisms are Smith, U.S. Pat. No. 3,176,811 and Osujo et al, U.S. Pat. No. 4,016,957.
The Smith, U.S. Pat. No. 3,176,811 is directed to a ball ramp actuated clutch that includes a Belleville spring washer 36 disposed between a ball ramp actuator and clutch discs 26. The ball ramp and disc arrangement of Smith is of course not a brake arrangement but illustrates a similar combination of components. For purposes of reviewing the prior art it is recognized that should the rotating driven member 14 be grounded, the ball ramp actuated disc arrangement 26 would then function as a brake. The Smith patent, however, offers no suggestion that a one-way clutch may be incorporated between one of the ball ramp members and an input shaft as will be seen to be the case in the invention of this application.
The patent to Smith also requires an externally positioned and operated clutch release member 44, 46, while no such external release is required by the invention of this application, in that the invention to be described hereinafter has a release mechanism designed internally which includes in combination a one-way clutch between a brake element and an input shaft.
The Osujo et al, U.S. Pat. No. 4,016,957 is directed to a ball ramp cam actuated disc brake. The Osujo et al patent is similar to the Smith patent in its teachings of a ball ramp actuated disc brake arrangement with an external brake release operated through lever 30. Osujo et al does not include a Belleville spring as is found in Smith and the invention of this application.
Osujo et al suffers the same basic deficiencies that Smith has in respect of the improvements present in the invention of this application, in that Osujo et al does not provide as the subject invention does, an internal brake release which includes in combination with a ball ramp actuated brake disc a one-way clutch disposed between an input shaft and a disc brake element.
The Smith and Osujo invention of this specification is additionally distinguished over, in that the ball ramp disc brake of the invention is actuated by a mechanism that counts the revolutions of an input shaft and upon the reaching of a pre-determined number of revolutions causes the actuation of the ball ramp arrangement.